This invention generally relates to vehicle suspension systems which include mechanism for tilting the vehicle's ground-engaging wheels in the direction of a turn, and deals more particularly with a system of the mentioned type in which the mechanism is automatically controlled by the vehicle's steering system.
Others have been aware for sometime of the importance of maintaining the upright attitude of a vehicle's wheels during the execution of a turn by the vehicle, and the use of wheel-tilting mechanisms for "banking" a vehicle's wheels into a turn, that is, tilting the wheels in the direction of the turn, is therefore an art-recognized concept. Also established in the art is the advantage of interconnecting the wheel-tilting mechanism with the vehicle's steering system, so that the latter may automatically operate the tilting mechanism during a turn executed by the vehicle; a typical arrangement of this type is shown in U.S. Pat. No. 2,652,263, issued Sept. 15, 1953 to Varnum.
Previous systems such as that shown by Varnum are operative to tilt the vehicle's wheels essentially equal amounts during any given turn of the vehicle, and perform satisfactorily only when the same magnitude of lateral force is acting on each of the wheels. Many vehicles, such as the common passenger automobile, are provided with rather loosely sprung suspension systems to minimize shock transmission and permit a smooth, comfortable ride; in vehicles of this type the vehicle tends to "lean" away from the direction of a turn due to body roll, and consequently, a portion of the vehicle's weight is transferred from the wheels tracking the inside path of the turn to the wheels tracking the outside path thereof. As a result of this additional weight imposed on the "outside" wheels (in addition to other factors), the lateral, inertial force acting upon the inside wheels is less than that acting upon the outside wheels so that the latter are caused to tilt outwardly (away from the direction of the turn) to a greater degree than that of the inside wheels. Inasmuch as prior art wheel-tilting arrangements are limited in their operation for tilting the inside and outside wheels in equal amounts, only the wheels associated with one side of the vehicle can be maintained in the desired vertical position, and the disparity between the attitudes of the inside and outside wheels is not corrected. Thus, there is a need in the art for a steering-system-controlled, wheel-tilting mechanism which not only simultaneously tilts the wheels on each side of the vehicle during a turn, but also compensates for the additional lateral force imposed on the outside tracking wheels by tilting the latter a greater degree than the inside wheels.
According to the present invention, a steering-system-controlled, wheel-tilting mechanism is provided for selectively tilting each of a pair of laterally spaced, steerable wheels, each of the latter being independently suspended upon a frame associated with the vehicle. Each wheel is provided with an axle assembly, including a mounting spindle for pivotally connecting an upper and lower swing arm between the vehicle's frame and the axle assembly to swingably mount the wheel on the vehicle. The upper swing arm is pivotally connected to a normally inclined control link portion of the upper extremity of an upwardly extending lever control arm which has central portions thereof pivotally connected to the frame while the other extremity thereof is pivotally connected to transversely shiftable steering linkage. Transverse shifting of the steering linkage during a turn produces pivotal movement of the lever control arm which, in turn, imparts rotational motion to the control link portion thereof. The control link portion of the lever control arm functions as a crank element to translate the rotational motion produced by the control arm during a turn to a linear, transverse movement which is communicated to the upper swing arm whereby to produce transverse shifting of the latter and effect the tilting of the wheels. The magnitude of transverse shifting of each of the upper swing arms is determined by the angle at which the control link portions are inclined from vertical. The control link portions of the control arms diverge from opposite sides of their respectively associated frame pivot points so that greater transverse displacement of the upper swing arm on the right side of the vehicle is effected, compared to the displacement of the left upper swing arm to produce greater compensating tilting of the right wheel than of the left wheel when the vehicle executes a left turn, and vice versa.
A primary object of the present invention is to provide a novel suspension system for a steerable, wheeled vehicle including especially simply mechanism controlled by the vehicle's steering system for tilting the steerable wheels of the vehicle during the execution of a turn by the latter in the direction of the turn in order to compensate for the effects of lateral forces acting upon the wheels and thereby maximize wheel traction and prolong tire life.
Another object of the invention is to provide mechanism of the mentioned type which includes linkage means to selectively tilt each of a pair of laterally spaced, steerable wheels differing degrees in the same direction in accordance with the differing magnitudes of lateral force respectively acting on such wheels.
A further object of the invention is to provide linkage of the mentioned type which functions to tilt the outside tracking wheel of the vehicle in the direction of a turn by the latter to a greater degree than the degree of tilt imposed upon the inside tracking wheel.
A still further object of the invention is to provide linkage means of the type described which also function in part to independently suspend each of the wheels on the vehicle's frame for swinging movement, but yet which do not affect the tilt attitude of the wheels unless the vehicle is executing a turn.
Another object of the present invention is to provide linkage means of the mentioned type, which include swing arms respectively associated with each of the wheels for carrying the latter on the vehicle's frame that are simultaneously transversely shiftable to produce tilting of the associated wheels.
Other and further objects of the invention will be made clear or become apparent in the course of the following description of a preferred embodiment of the invention.